Polarized materials include ferroelectric and magnetic materials. For purposes of this discussion, polarized materials will include any material capable of being polarized, whether they are currently polarized or not. The material has a polarization of one state or the opposite state, such a positive or negative polarity. The polarization state often depends upon the nature of the polarizing force applied. For example, ferroelectric materials will assume a positive or negative polarization with application of an electric field. In some materials, application of a positive electric field will cause the material to assume a positive polarity. In many polarizable materials, the hysteresis loop of the material exhibits a non-linear slope during the application of the forcing function.
Once a polarized cell has been polarized to a particular state, and that state is correlated to a ‘one’ or a ‘zero,’ that data will be retained for a period of time and in some cases indefinitely. However, current techniques for sensing the state of the cell are ‘destructive’ in that the sensing operation causes the cells to assume one of the two states, nominally the ‘zero’ state. A charge release caused by the forcing of the cell to the ‘zero’ state is the mechanism sensed to determine the state of the cell. For example, if a ‘one’ state is of positive polarity, the cell is switched to negative polarity and the charge released is sensed. However, in the process, the data state changed from ‘one’ to ‘zero.’ For ‘zero’ state cells, the cell does not change states. However, in order to preserve the data in the cells in the one state, the data must be stored and rewritten into the cells after the read cycle. This is time consuming, power consuming and inefficient.
Therefore, it would be useful to have a robust, non-destructive means for sensing the polarization state of polarized materials.